Remove AfdoAdditionalProfileDirs product variable

AfdoAdditionalProfileDirs is unconnected to build/make/core/soong_config.mk and is currently unused. Removing AfdoAdditionalProfileDirs will cut down on complexity when we migrate the support of auto-fdo profiles to Bazel cc rules.

b/258684450 proposes an alternative to support the use cases that were meant to be supported by AfdoAdditionalProfileDirs.

Test: existing go tests
Bug: 253540178
Change-Id: I024e48598a560717a1d6c19b16bde3fe65ff1961
diff --git a/cc/afdo.go b/cc/afdo.go
index fb66bbe..d36f4af 100644
--- a/cc/afdo.go
+++ b/cc/afdo.go
@@ -36,7 +36,7 @@
 
 func getAfdoProfileProjects(config android.DeviceConfig) []string {
 	return config.OnceStringSlice(afdoProfileProjectsConfigKey, func() []string {
-		return append(globalAfdoProfileProjects, config.AfdoAdditionalProfileDirs()...)
+		return globalAfdoProfileProjects
 	})
 }